The present invention relates to a process for the preparation of monoacetalized glyoxal
1. Field of the Invention
The present invention relates to a process for the preparation of monoacetalized glyoxal of the general formula I: ##STR2## wherein either R.sub.1 and R.sub.2, which are identical, represent a --CHRR.sub.3 group, in which R and R.sub.3, which are identical or different, represent an alkyl, alkenyl or aralkyl group, or R.sub.1 and R.sub.2, which are identical, represent a --CH.sub.2 R group, in which R represents a hydrogen atom, an alkyl, alkenyl or aralkyl radical, or R.sub.1 and R.sub.2 together form a --CH.sub.2 --(CRR).sub.n --CHR-- radical, in which n represents 0 or 1 and R retains the meaning given previously.
As examples of the --CH.sub.2 --(CRR).sub.n --CHR-- radical it is possible to mention the ethylene, propylene, trimethylene, 2,2-dimethyl-propane-1,3-diyl groups, etc.
2. Description of the Prior Art
The reactions of glyoxal with alcohols have been studied extensively and they make it possible to have easy access to the corresponding glyoxal bisacetal (U.S. Pat. No. 2,194,405; GB Pat. No. 559.362; French Pat. Nos. 1.280.792 and 2.284.584; H. Fischer et al, Chem. Ber., 1926, 59, 851; D. H. Grangaard et al, J. Amer. Chem. Soc. 1939, 61, 428 and 755; M. Sprung et al, J. Amer. Chem. Soc., 1951, 73 1884; H. Fiesselmann et al, Chem. Ber., 1954, 87, 906; U. Faas et al, Chem. Ber. 1954, 87, 1343; J. M. Kliegman et al, J. Org. Chem., 1972, 37, 1276; ibid 1973, 38, 556; ibid 1974, 39, 1172; F. Chastrette et al, Bull. Soc. Chim. France, 1976, 601 and 613).
These direct methods have not made it possible to have access to glyoxal monoacetals, even though indirect methods have been used to obtain them, such as ozonolysis of the corresponding acetal of acrolein or the oxidizing cleavage of an .alpha.,.beta. dihydroxylated acetal, such as 2,3-dihydroxy-1,1,4,4-tetraethoxy butane (C. Harries, Chem. Ber., 1903, 36, 1933; H. Fischer et al, Helv. Chim. Acta., 1939, 18, 514; L. Yanovkaya et al, Izvest. Akad. Nauk SSR, Otdel Khim. Nauk. 1963, 857; J. Hine et al, J. Amer. Chem. Soc., 1972, 94, 6998; P. Noire, Chemical Abstracts, 1978, 89, reference 215108).
These processes are long, difficult and sometimes even dangerous when they are applied to substantial amounts (cf. German Federal Republic Pat. No. 3.346.266).